The present invention relates generally to apparatus for receiving and transmitting powdered or granular materials such as for example sand, cement, gravel or the like and more particularly to such apparatus which is specifically designed to provide a continuous pressurized supply of such materials in either a dry or wet form.
There exist a wide variety of applications wherein it is desirable to be able to transport powdered or granular materials or mixtures thereof with water in a substantially continuous manner through suitable conduit means for placement at a remote worksite. Such applications may range from placement of concrete in the construction of various types of wall, roof or floor structures such as swimming pools, tunnels or of refractory materials or to the transporting of gravel or crushed stone to a roof deck.
Various types of appartus have been developed over the years in an effort to handle the variety of available materials in either wet or dry form and yet still be economical in both cost of manufacture as well as operation thereof. Generally, the prior apparatus may be categorized as either tank type or rotary type.
Tank type apparatus tend to be expensive to manufacture and to operate and are rather limited in the types of work for which they are suited. Further, they tend to be prone to clogging at the tank outlet when used for "dry mix" applications particularly when the sand is too damp. However, if the sand used in the mix is dried to too great a degree before use, excessive "fall off" of the material when sprayed will occur. Also, as water is normally added at the nozzle end of the conduit in such applications, there seems to be insufficient time for absorption thereof by the cement which may result in excessive shrinkage cracking of the finished work. In order to overcome those problems it is often necessary to employ a separate predampener to add the proper moisture to the mixture prior to being placed in the tank.
Rotary type apparatus on the other hand tend to be much less expensive to build and operate but often require a relatively high degree of maintenance due to the problems associated with wear resulting from incursion of the powdered or granular materials. The problem of clogging is often encountered in the rotary type machines as well.
It is also noted that prior apparatus of this type has generally not been well suited for the introduction of the various types of additives be they in the form of liquids such as synthetic rubber emulsions (latex) or solids such as steel or polymeric composition fibers. While it has been possible to introduce the various liquid or powdered admixtures into the material prior to processing through the respective apparatus, the introduction of such additives as polymeric and particularly steel fibers therein results in greatly increased wear and tear on the various valves and seals provided therein.
The present invention overcomes these problems in providing a concrete material feed apparatus which is particularly well suited for a wide variety of applications be it wall, roof or floor construction by wet or dry mixtures of granulated or powdered materials. Further, the present apparatus is well suited to accommodate the introduction of virtually any type of additives, such as solids, liquids, or gases into the mixture without appreciable increase in the wear or resulting life expectancy of the various components. The present invention provides a plurality of stationary charging chambers each of which is successively filled with material from a supply hopper by gravity flow via a rotating valve assembly which thereafter operates to air pressurize the chambers and eject the material therein into a central mixing chamber. The shape and contour of the respective charging chambers as well as the location of the openings for admission of pressurized fluid thereto are particularly designed to assure a smooth clog-free flow of material into the central mixing chamber without regard to the moisture content thereof. Further, agitators are provided within the hopper so as to assure free flow of material into the respective charging chambers.
The central mixing chamber is also provided with conduit means in fluid communication therewith which are well suited for conducting virtually any type of additive to the mixture immediately prior to its being supplied to the distribution conduit. In this manner the additives bypass the various critical moving valving components of the apparatus and the potentially excessive wear and tear generated thereby is all but eliminated. Further, not only does the ability to inject the majority of the water into the mixing chamber versus adding it at the discharge nozzle afford a greater time period to assure proper hydration of the cement, but the provision of a central mixing chamber also aids in insuring a smoother steadier non-pulsating flow of material to the operator's nozzle.
It should also be noted that the design of the present apparatus is not only well suited to provide long, efficient trouble-free operation but also replacement of the component moving parts which are held to a minimum is greatly facilitated thereby. Thus, not only is the present invention well suited for a variety of applications, it is also designed to provide cost savings both in terms of manufacturing as well as operation thereof.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.